(Topic ID: 191374)

Gottlieb system 80 mpu problem.


By Moto_bone

2 years ago



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  • 25 posts
  • 6 Pinsiders participating
  • Latest reply 2 years ago by Moto_bone
  • Topic is favorited by 2 Pinsiders

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#1 2 years ago

Hello everyone!

I'm working on a black hole that I picked up in non working condition.

Looks to have set for a very long time.

I did all ground mods to all the board's and a new power cord. I removed the battery and corrosion damaged parts from the mpu and cleaned the board and repopulated the components.

The game boots, I can play, sounds and speech are functioning.

I am having a problem with the battery backup. I have this same problem with and without battery connected.

I've got "8" credits all the time and the high score is "888888".

Is this a possible 5101 fault?

Any info would be great!

Thanks! -Matt

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#2 2 years ago

It might be that one of the address lines is stuck high. 8 is only one bit off from zero. If you can, probe the four data likes coming from the ram

#3 2 years ago

Is your black wire touching the red wire rail?

#4 2 years ago
Quoted from donjagra:

Is your black wire touching the red wire rail?

It looks that way but it's not shorting. I'll change that though.

Thanks for the extra eyes.

#5 2 years ago
Quoted from zacaj:

It might be that one of the address lines is stuck high. 8 is only one bit off from zero. If you can, probe the four data likes coming from the ram

Any way to test that without a logic probe or scope? You are talking about the 5101 ram yes?

#6 2 years ago
Quoted from Moto_bone:

Any way to test that without a logic probe or scope? You are talking about the 5101 ram yes?

Yeah, but it might not be the ram itself. Could be the signal line between it. You could try testing continuity from each of the data lines to 5v and ground, maybe? If you've got a spare 5101 I'd just socket it though

#7 2 years ago
Quoted from zacaj:

Yeah, but it might not be the ram itself. Could be the signal line between it. You could try testing continuity from each of the data lines to 5v and ground, maybe? If you've got a spare 5101 I'd just socket it though

Ok, I don't have an easily available spare but I do have a spare mpu that I could desolder it from!

I'll inspect the board really well to see if I can find any broken traces as well.

Thanks!

#8 2 years ago

I'm working on removing the 5101 from my spare board right now but for !#&$'s and grins, I did the system test "20" and it shows 5101.. Go figure.

#9 2 years ago

I had a 80b mpu with a bad 5101 earlier this week. Wouldn't keep credits/scores/audits. Mpu self test came back 'ok' even though the 5101 was bad.

#10 2 years ago
Quoted from gutz:

I had a 80b mpu with a bad 5101 earlier this week. Wouldn't keep credits/scores/audits. Mpu self test came back 'ok' even though the 5101 was bad.

Ok, well put the 5101 in to the good board. Still no go. Guess it's a possibility I had 2 bad 5101's..

I verified I'm getting 4v on pin 22. Now what?

On a side note, I can start the game and play. Soon as I game over, it goes right back to 8 credits.

#11 2 years ago

Did you check continuity from the Data Pins of the 5101 to the CPU? An open trace could cause a single bit to go high (D3=1).

#12 2 years ago

Check the connectors on the right side of the MPU board. It could just be a loose connector or bad connection. I was having similar display problems when I first switched over to the Rottendog board because it was thicker and the connectors didn't line up as well.

1 month later
#13 2 years ago
Quoted from CactusJack:

Did you check continuity from the Data Pins of the 5101 to the CPU? An open trace could cause a single bit to go high (D3=1).

I checked continuity, on the data lines. No breaks. I put a new 5101 in still the same thing.

8 credits, and a high score of "888888" that won't clear. As soon as you drain the last ball in play it automatically goes right back to 8 credits.

Could this be a bad 6502?

#14 2 years ago

On a side note, I'm ordering a logic probe so I can test these TTL and CMOS chips.

#15 2 years ago
Quoted from Moto_bone:

I checked continuity, on the data lines. No breaks. I put a new 5101 in still the same thing.
8 credits, and a high score of "888888" that won't clear. As soon as you drain the last ball in play it automatically goes right back to 8 credits.
Could this be a bad 6502?

Probably not. It'd be messing with every other read too. The rest of the game works fine right?

Maybe the line is shorted high?

#16 2 years ago
Quoted from zacaj:

Probably not. It'd be messing with every other read too. The rest of the game works fine right?
Maybe the line is shorted high?

Yea, rest of the game works. Just this one problem I can't figure out.

#17 2 years ago
Quoted from zacaj:

Probably not. It'd be messing with every other read too. The rest of the game works fine right?
Maybe the line is shorted high?

Any idea of what Z4 and Z36 does in the circuit. I see it is outputting to pin 17 and 19 of the 5101.

#18 2 years ago

Chip enable perhaps? Could this cause my problem?

#19 2 years ago
Quoted from Moto_bone:

Chip enable perhaps? Could this cause my problem?

I doubt chip enable would do this. If that wasn't working then your whole ram wouldn't work. Other stuff gets saved, right?

#20 2 years ago

I don't think any settings are getting saved but I'll verify that tonight when I'm at the machine.

I do get a 5101 error while doing a system self test. I'm thinking the chip enable isn't high so the chip isn't even recognized as being in circuit.

#21 2 years ago

Matt

Could it be that the credit and high score is actually zero but just being displayed as 8s. In which case is it a display problem and not the 5101?

Can you start a game when the machine is showing 8 credits or do you have to add more credits to be able to play?

Andy

#22 2 years ago
Quoted from Andy_B:

Matt
Could it be that the credit and high score is actually zero but just being displayed as 8s. In which case is it a display problem and not the 5101?
Can you start a game when the machine is showing 8 credits or do you have to add more credits to be able to play?
Andy

I can start a game with no battery attached. I can actually start a 4 player game which will bring the credits display down to "4". Soon as the last ball drains from the 4th player, it will automatically go back to "8" credits.

Nice feature lol.

#23 2 years ago

Well everyone! I fixed the problem! After studying the schematic for awhile and reading over the 5101 specs. Pin 17 is the chip enable for low power mode and pin 19 is the chip enable pin. I decided to swap out z36 (4069) which feeds pin 19 on the 5101. Bingo! I now have no free credits and high score isn't showing "888888".

Thanks for everyone's help!

#24 2 years ago

Glad you got it solved! Perseverance prevails!

#25 2 years ago
Quoted from CactusJack:

Glad you got it solved! Perseverance prevails!

It is always a good feeling when you finally troubleshoot the electronics yourself!

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